import time 
scale = 50
print("执行开始".center(scale//2, "-")) 
start = time.perf_counter() 
for i in range(scale+1): 
    a = '*' * i 
    b = '.' * (scale - i) 
    c = (i/scale)*100 
    dur = time.perf_counter() - start 
    print("\r{:^3.0f}%[{}->{}]{:.2f}s".format(c,a,b,dur),end='') 
    time.sleep(0.1) 
print("\n"+"execute end".center(scale//2,'-'))
